const fs = require("fs")
const path = require("path")
const paths = require("./paths")
// @ts-ignore
const chalk = require("react-dev-utils/chalk")
const resolve = require("resolve")

/**
 * Get additional module paths based on the baseUrl of a compilerOptions object.
 *
 * @param {{baseUrl?: string | null }} options
 */
function getAdditionalModulePaths(options = {}) {
  const baseUrl = options.baseUrl

  // We need to explicitly check for null and undefined (and not a falsy value) because
  // TypeScript treats an empty string as `.`.
  if (baseUrl == null) {
    // If there's no baseUrl set we respect NODE_PATH
    // Note that NODE_PATH is deprecated and will be removed
    // in the next major release of create-react-app.

    const nodePath = process.env.NODE_PATH || ""
    return nodePath.split(path.delimiter).filter(Boolean)
  }

  const baseUrlResolved = path.resolve(paths.appPath, baseUrl)

  // We don't need to do anything if `baseUrl` is set to `node_modules`. This is
  // the default behavior.
  if (path.relative(paths.appNodeModules, baseUrlResolved) === "") {
    return null
  }

  // Allow the user set the `baseUrl` to `appSrc`.
  if (path.relative(paths.appSrc, baseUrlResolved) === "") {
    return [paths.appSrc]
  }

  // If the path is equal to the root directory we ignore it here.
  // We don't want to allow importing from the root directly as source files are
  // not transpiled outside of `src`. We do allow importing them with the
  // absolute path (e.g. `src/Components/Button.js`) but we set that up with
  // an alias.
  if (path.relative(paths.appPath, baseUrlResolved) === "") {
    return null
  }

  // Otherwise, throw an error.
  throw new Error(
    chalk.red.bold(
      "Your project's `baseUrl` can only be set to `src` or `node_modules`." +
        " Create React App does not support other values at this time.",
    ),
  )
}

/**
 * Get webpack aliases based on the baseUrl of a compilerOptions object.
 *
 * @param {{baseUrl?: string | null}} options
 */
function getWebpackAliases(options = {}) {
  const baseUrl = options.baseUrl

  if (!baseUrl) {
    return {}
  }

  const baseUrlResolved = path.resolve(paths.appPath, baseUrl)

  if (path.relative(paths.appPath, baseUrlResolved) === "") {
    return {
      src: paths.appSrc,
    }
  }
}

/**
 * Get jest aliases based on the baseUrl of a compilerOptions object.
 *
 * @param {{baseUrl?: string | null}} options
 */
function getJestAliases(options = {}) {
  const baseUrl = options.baseUrl

  if (!baseUrl) {
    return {}
  }

  const baseUrlResolved = path.resolve(paths.appPath, baseUrl)

  if (path.relative(paths.appPath, baseUrlResolved) === "") {
    return {
      "^src/(.*)$": "<rootDir>/src/$1",
    }
  }
}

function getModules() {
  // Check if TypeScript is setup
  const hasTsConfig = fs.existsSync(paths.appTsConfig)
  const hasJsConfig = fs.existsSync(paths.appJsConfig)

  if (hasTsConfig && hasJsConfig) {
    throw new Error(
      "You have both a tsconfig.json and a jsconfig.json. If you are using TypeScript please remove your jsconfig.json file.",
    )
  }

  /** @type {{compilerOptions?: object }} */
  let config = {}

  // If there's a tsconfig.json we assume it's a
  // TypeScript project and set up the config
  // based on tsconfig.json
  if (hasTsConfig) {
    const ts = require(resolve.sync("typescript", {
      basedir: paths.appNodeModules,
    }))
    config = ts.readConfigFile(paths.appTsConfig, ts.sys.readFile).config
    // Otherwise we'll check if there is jsconfig.json
    // for non TS projects.
  } else if (hasJsConfig) {
    config = require(paths.appJsConfig)
  }

  const options = config.compilerOptions || {}

  const additionalModulePaths = getAdditionalModulePaths(options)

  return {
    additionalModulePaths,
    webpackAliases: getWebpackAliases(options),
    jestAliases: getJestAliases(options),
    hasTsConfig,
  }
}

module.exports = getModules()
